System for performing posterior spinal arthrodesis at a facet joint

Abstract

The system for performing posterior spinal arthrodesis at a facet joint comprises an implant device (1) and its retaining means (2). The implant device (1) is in the form of an element comprising an opening (12) for receiving a bone graft and is intended to be introduced into a cavity (5) previously produced at the location of the facet joint to be immobilized, while the retaining means is in the form of a transfacet screw (2) for compressing the implant (1) in the cavity, comprising a threaded distal part (20) intended to be screwed at least into the bone material (3) downstream of the implant (1), its proximal part (21) being shaped to produce, at the bone material (4) upstream of the implant (1), a bearing surface bearing against or within said bone material (4).

Description

[0001] [TITLE: System for performing spinal arthrodesis via the posterior approach at the level of a facet joint

[0002] The present invention relates to a system for performing spinal arthrodesis via the posterior route at the level of a facet joint, said system comprising an implant device and its retaining means.

[0003] Such an intervention, carried out via the posterior approach, makes it possible to immobilize two vertebrae by fusing each of the lower articular processes of a vertebra with the upper articular process opposite the neighboring lower vertebra through the insertion into the interface space of a cage-type implant device containing a bone graft.

[0004] In practice, the surgeon prepares the implant location by removing the joint capsule using an instrument called a facet chisel, then uses a rasp to "bleed" the parts opposite the joint space on the facets. This step with the rasp has two purposes: to prepare the pre-existing space, with a boneless, but often slightly curved, joint space, to the straight shape of the implant, and to promote the subsequent fusion of the facets through the implant by having bled / revived the facets until reaching the cancellous bone.

[0005] Implant devices are already known for carrying out such an intervention, which consist of a wedge-shaped element, the two opposite faces of which, each intended to come into contact with a facet, have a surface provided with reliefs to ensure anchoring, and which is pierced with a multiplicity of holes intended for the development of the bone material after deposition of a bone graft. However, the wedge shape, despite the reliefs, tends not to prevent expulsion, so these implant devices are associated with at least one screw, passing through said implant device through a hole and screwed into an apophysis obliquely relative to the median plane of the implant. Document WO 2012154653 describes such an implant device, provided with two screws.However, due to the low inclination of the screw axes, these are practically parallel to the said median plane, so that there is little bone material between the screws and the walls of the facets, which are then weakened, and consequently the fixation is less certain.

[0006] Also known, from document WO2019016341 in the name of the present Applicant, is an implant device which is in the form of a flat element, of constant thickness, comprising, for receiving a bone graft, a large central opening giving it a substantially annular shape, and intended to be introduced into a cavity previously made at the location of the facet joint to be immobilized, said element having a D shape, the rounded side constituting the distal edge for introduction into said cavity, while the opposite, rectilinear proximal edge, comprises a means of securing to a holding and positioning tool, while the opposite faces of said flat element comprise reliefs which consist of notches arranged perpendicular to the direction of introduction, each of the notches having a tooth profile with two sides, one of which,the one oriented on the side of said proximal edge is perpendicular or substantially perpendicular to the main plane of said element, while the other side is inclined.

[0007] The constant thickness is intended to overcome the disadvantages of a wedge shape and, in association with the notches, to prevent expulsion, and thus eliminate the need for screws.

[0008] However, despite this, it was found that expulsion could occur.

[0009] The aim of the present invention is to propose a system for performing spinal arthrodesis via the posterior route at the level of a facet joint, comprising an implant device and its retaining means, making it possible to avoid expulsion, without resorting to screws for fixing said implant device in the bone material, as well as to optimize its maintenance.

[0010] The system for performing spinal arthrodesis by the posterior route at the level of a facet joint comprising an implant device and its retaining means according to the invention, is characterized in that said implant device is in the form of an element comprising, for receiving a bone graft, at least one opening or notch open on the proximal side and closed on the distal side, and intended to be introduced into a cavity previously made at the location of the facet joint to be immobilized, the opposite faces of said element, comprising reliefs, and in that said retaining means is in the form of a transfacet screw making it possible to compress said implant in said cavity, namely that it comprises a threaded distal part of transverse dimensions allowing it to pass into said opening or notch,so as to allow the passage in the latter of said compression screw to be screwed at least into the bone material downstream of said implant, while its proximal part is shaped to produce at the level of the bone material upstream of said implant a support against or in the latter.,

[0011] It will be understood that after introduction of the implant into the cavity previously created at the location of the facet joint to be immobilized, a hole is made in the apophyses passing through said implant through its opening or its notch, then the compression screw is screwed in, which is then trapped in the opening or behind the distal closure of the notch, thus preventing movement in the direction of expulsion.

[0012] According to an additional characteristic of the system according to the invention, the implant device is in the form of a flat element, of constant thickness.

[0013] According to an alternative embodiment of the system according to the invention, the implant device has a curved shape.

[0014] Such a shape is intended to adapt to the curvature of the facet joint, without the need for significant rectification of the interface space.

[0015] According to another additional feature of the system according to the invention, the implant device has flexibility characteristics. This feature allows the implant device to adapt to the curvature of the facet joint, whether or not it is curved.

[0016] According to another additional characteristic of the system according to the invention, the reliefs of the opposite faces of the implant device consist of notches arranged perpendicular to the direction of introduction, each of the notches having a tooth profile with two sides, one of which, the one oriented towards the proximal edge, is perpendicular or substantially perpendicular to the main plane of said implant device.

[0017] According to another additional characteristic of the system according to the invention, the implant device comprises a single opening, giving it a substantially annular shape.

[0018] According to a variant of the system according to the invention, the implant device has a U shape, delimiting a notch between its two branches, the transverse part connecting the two branches being positioned on the distal introduction side.

[0019] According to a first particular embodiment of the system according to the invention, the screw has a non-constant thread, and more particularly this pitch is at the level of the proximal part lower than that of the distal part, each in one of the articular processes to be connected.

[0020] In addition to retaining the implant, the compression screw generates the rapprochement of the two apophyses and the clamping of said implant, so as to increase its primary anchoring and promote bone fusion.

[0021] Advantageously, such a screw does not have a head, and can be completely buried in the bone material.

[0022] According to an additional characteristic of the first particular embodiment of the system according to the invention, the screw comprises between the two proximal and distal parts, a smooth section.

[0023] According to another additional characteristic of the first particular embodiment of the system according to the invention, the proximal part of the screw has a diameter greater than that of the distal part. According to another additional characteristic of the first second particular embodiment of the system according to the invention, the threads of the proximal and distal parts of the screw each comprise a tapping notch.

[0024] According to a second particular embodiment of the system according to the invention, the proximal part of the screw consists of a head capable of bearing against the bone material, while the distal part is screwed into the bone material downstream of the implant.

[0025] According to an additional characteristic of the second particular embodiment of the system according to the invention, the compression screw comprises a smooth section under the head, at the level of its part intended to pass through the bone material upstream of the implant.

[0026] The smooth section facilitates compression, due to the traction achieved by screwing the threaded part into the bone material downstream of the implant.

[0027] It should be noted that the distal part can be entirely threaded, the achievement of compression then requiring that the hole made in the bone material upstream of the implant be of a diameter greater than that of said threaded distal part and less than that of the head.

[0028] The advantages and characteristics of the system according to the invention will emerge more clearly from the description which follows and which refers to the attached drawing, which represents non-limiting embodiments thereof.

[0029] In the attached drawing: Figure 1 represents a perspective view of a first embodiment of the system according to the invention,

[0030] - figure 2 represents a schematic sectional view of the same system placed between two apophyses,

[0031] - Figure 3 represents a schematic sectional view of the same system, from another angle, according to arrow A of Figure 2, Figure 4 represents a schematic sectional view of a second embodiment of the system according to the invention. With reference to Figure 1, it can be seen that the system according to the invention comprises an implant device 1 and a screw 2.

[0032] The implant device 1 shown consists, without limitation, of an implant device conforming to that described in document WO 2019016341, namely that it is in the form of a substantially flat element, and which has the shape of a D, intended to be introduced between two apophyses to replace the joint capsule. It thus comprises an introduction side, distal 10, of rounded shape and a rectilinear proximal side 11, as well as a central opening 12 which gives it a generally annular shape.

[0033] On the other hand, each of its two faces 13 and 14, of which only face 13 is visible in this figure 1, is provided with notches 15 aligned transversely with respect to the introduction axis, and intended for the creation of an anchoring in the bone material.

[0034] According to a first embodiment, the screw 2 consists of a compression screw, which for this purpose has a thread of non-constant pitch, that is to say that it comprises a threaded distal part 20 and a proximal part 21 also threaded, separated by a smooth section 22, while the pitch of the thread of the proximal part 21 is smaller than the pitch of the thread of the distal part 20. On the other hand, it can be seen that the diameter of the screw 2 is smaller than the dimensions of the opening 12.

[0035] Note that the smooth section 22 is optional, it can be replaced by a threaded transition zone, allowing you to move from one pitch to another.

[0036] It will also be noted that the threads of the distal 20 and proximal 21 parts are preferably provided with tapping notches, respectively 23 and 24. Furthermore, the proximal part 21 has a diameter greater than that of the distal part 20, so that its thread cuts a different thread in the bone material from that cut upstream by the thread of the distal part 20.

[0037] Referring now to Figures 2 and 3, we can see the installation of the system according to the invention, at the level of one of the two facet joints of two vertebrae, and more particularly, seen posteriorly, the articulation between the left apophysis 3 of a vertebra and the left apophysis 4 of the adjacent vertebra positioned below. Knowing that the right side is treated in an identical manner.

[0038] In previous steps not shown, the two processes 3 and 4 are prepared, namely that the joint capsule as well as the osteophytes have been removed, then the facet joint space is opened to create a cavity 5 at the level of the interface space which is further revived by means of a rasp until reaching the spongy bone in order to prepare for a good subsequent fusion.

[0039] In Figures 2 and 3, implant 1 has been introduced into cavity 5 in the direction of arrow B, and it fits tightly there.

[0040] It should be noted that from a technical surgical point of view, the introduction of implant 1 on the right side is carried out simultaneously on the left side, knowing that in the case of successive introductions, the first introduction would tend to close the interface space on the other side.

[0041] It should also be noted that before the introductions, a bone graft G will have been placed in opening 12.

[0042] We can also see in these figures that the installation of implant 1 is completed by that of screw 2, knowing that a hole will have been previously drilled in the lower process 4 then in the upper process 3, passing through the opening 12 of implant 1, possibly with a targeting device.

[0043] The screw 2 is then screwed into this hole, which on the one hand prevents the expulsion of the implant 1, but also, due to the difference in pitch of the threads of the distal 20 and proximal 21 parts, allows the processes 3 and 4 to be tightened on the implant 1 and more particularly the notches 15 thereof, and thus ensures perfect support and promotes bone fusion.

[0044] In figures 2 and 3, the screw 2 is perfectly perpendicular to the main plane of the implant 1, this is however a special case since the insertion axis of the screw 2 can perfectly make an angle with this plane. The drilling being carried out blindly after introduction of the implant 1, the opening 12 preferably, but not limited to, has large dimensions compared to the transverse dimensions of the screw 2, so as to leave a large latitude when a sighting device is not used.

[0045] It will also be noted that, to the extent that a high-performance aiming device can be used, it may be envisaged that the opening 12 can be tapped, in order to allow screwing of the distal part 20, the thread of which is then extended and total or partial replacement of the smooth section 22.

[0046] Referring now to Figure 4, a second embodiment of the system according to the invention can be seen.

[0047] This differs from the first in that the proximal part 21 of the screw 2 consists of a head 25 capable of bearing against the apophysis 4, while the distal part 20 is threaded and connected to the head 25 by a smooth section 22 intended to be arranged in the apophysis 4, so as to be able to carry out the compression, namely the tightening of the apophyses 3 and 4 on the implant 1.

[0048] It will be noted that for the purpose of burying the head 25 in the bone material, this head 25 can be milled.

Claims

Re vendicat ions 1) [System for performing spinal arthrodesis via the posterior route at the level of a facet joint comprising an implant device (1) and its retaining means (2), characterized in that said implant device (1) is in the form of an element comprising, for receiving a bone graft (G), at least one opening (12) or a notch open on the proximal side and closed on the distal side, and intended to be introduced into a cavity (5) previously made at the location of the facet joint to be immobilized, the opposite faces (13, 14) of said element comprising reliefs (15), and in that said retaining means is in the form of a transfacet screw (2) allowing the compression of said implant (1) in said cavity, namely that it comprises a threaded distal part (20) of transverse dimensions allowing it to pass into said opening (12) or notch, so as to allow the passage in the latter of said screw (2) to be screwed at least into the bone material (3) downstream of said implant (1), while its proximal part (21) is shaped to produce at the level of the bone material (4) upstream of said implant (1) a support against or in the latter. 2) System according to claim 1, characterized in that the implant device (1) is in the form of a flat element of constant thickness. 3) System according to claim 1, characterized in that the implant device (1) has a curved shape. 4) System according to any one of claims 1 to 3, characterized in that the implant device (1) has flexibility characteristics. 5) System according to any one of claims 1 to 4, characterized in that the reliefs of the opposite faces (13, 14) of the implant device (1) consist of notches (15) arranged perpendicular to the direction of introduction (B), each of the notches (15) having a two-sided tooth profile, one of which, the one oriented towards the proximal edge (11), is perpendicular or substantially perpendicular to the main plane of said implant device (1). 6) System according to any one of claims 1 to 5, characterized in that the implant device (1) has a single opening (12), giving it a substantially annular shape. 7) System according to any one of claims 1 to 5, characterized in that the implant device (1) has a U shape, delimiting between its two branches a notch, the transverse part connecting the two branches being positioned on the distal introduction side. 8) System according to any one of claims 1 to 7, characterized in that the screw (2) has a non-constant thread, and more particularly this pitch is at the level of the proximal part (21) less than that of the distal part (20), each of said proximal (21) and distal (20) parts being intended to be screwed into one of the articular processes (3, 4) to be connected. 9) System according to claim 8, characterized in that the screw (2) comprises between the two proximal (21) and distal (20) parts, a smooth section (22). 10) System according to claim 8 or claim 9, characterized in that the proximal part (21) of the screw (2) has a diameter greater than that of the distal part (20). 11) System according to any one of claims 8 to 10, characterized in that the threads of the distal (20) and proximal (21) parts of the screw (2) each comprise a tapping notch (23, 24). 12) System according to any one of claims 1 to 7, characterized in that the proximal part (21) of the screw (2) consists of a head (25) capable of bearing against the material bone (4), while the distal part (20) is screwed into the bone material (3) downstream of the implant (1). 13) System according to claim 12), characterized in that the screw (2) comprises a smooth section (22) under the head (25), at the level of its part intended to pass through the bone material (4) upstream of the implant (1). |

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